diff --git a/meridian/analysis/formatter.py b/meridian/analysis/formatter.py
index 721024a..a20f516 100644
--- a/meridian/analysis/formatter.py
+++ b/meridian/analysis/formatter.py
@@ -110,6 +110,24 @@ def bar_chart_width(num_bars: int) -> int:
   return (c.BAR_SIZE + c.PADDING_20) * num_bars
 
 
+def format_percent(percent: float) -> str:
+  """Formats a percentage value into a string format.
+
+  Percentage values between 0 and 1 are formatted with 1 decimal place.
+  Percentage values greater than 1 are formatted with 0 decimal places.
+
+  Args:
+    percent: The percentage value to format.
+
+  Returns:
+    A formatted string.
+  """
+  if percent >= 0.01:
+    return '{:.0%}'.format(percent)
+  else:
+    return '{:.1g}%'.format(percent * 100)
+
+
 def compact_number(n: float, precision: int = 0, currency: str = '') -> str:
   """Formats a number into a compact notation to the specified precision.
 
diff --git a/meridian/analysis/formatter_test.py b/meridian/analysis/formatter_test.py
index b54bb4e..44fb0c3 100644
--- a/meridian/analysis/formatter_test.py
+++ b/meridian/analysis/formatter_test.py
@@ -41,6 +41,16 @@ def test_bar_chart_width(self):
     width = formatter.bar_chart_width(num_bars)
     self.assertEqual(width, 186)
 
+  @parameterized.named_parameters(
+      ('zero_percent', 0.0, '0%'),
+      ('less_than_one_percent', 0.0005, '0.05%'),
+      ('one_percent', 0.01, '1%'),
+      ('greater_than_one_percent', 0.4257, '43%'),
+  )
+  def test_format_percent_correct(self, percent, expected):
+    formatted_percent = formatter.format_percent(percent)
+    self.assertEqual(formatted_percent, expected)
+
   def test_compact_number_expr_default(self):
     expr = formatter.compact_number_expr()
     self.assertEqual(expr, "replace(format(datum.value, '.3~s'), 'G', 'B')")
diff --git a/meridian/analysis/summarizer.py b/meridian/analysis/summarizer.py
index 395bd23..57fc123 100644
--- a/meridian/analysis/summarizer.py
+++ b/meridian/analysis/summarizer.py
@@ -227,8 +227,8 @@ def _slice_table_by_evaluation_set(eval_set: str) -> Sequence[str]:
         ]
         row_values = [
             '{:.2f}'.format(sliced_table_by_eval_set[c.R_SQUARED].item()),
-            '{:.0%}'.format(sliced_table_by_eval_set[c.MAPE].item()),
-            '{:.0%}'.format(sliced_table_by_eval_set[c.WMAPE].item()),
+            formatter.format_percent(sliced_table_by_eval_set[c.MAPE].item()),
+            formatter.format_percent(sliced_table_by_eval_set[c.WMAPE].item()),
         ]
         return row_values